A microwave apparatus was designed and constructed to study the effect of localized hyperthermia on tumor growth, the biochemical alterations produced by hyperthermia, and the therapeutic effectiveness of combining chemotherapy with local hyperthermia. In a study to compare the anti-tumor properties of PALA (NSC-224131) in a spectrum of transplantable tumors in mice, PALA was found to be highly active against most solid tumors but to possess only minimal activity against several rapidly growing leukemias. The adenosine deaminase inhibitor, 2'-deoxycoformycin, was found to potentiate the cytotoxic and antitumor activity of several adenosine analogues that are substrates for adenosine deaminase and that are inactivated by this enzyme. In addition, 2'-deoxycoformycin exhibited immunosuppressive activity in several experimental systems. A limited study was conducted comparing the potentiating effects of 2'-deoxycoformycin and EHNA on the cytotoxic properties of xylosyladenine.